1. Field of the Invention
This present invention relates to a system and method for control of electrically operated parking brake-by-wire systems, and more particularly to a method and system for controlling the operation of electrically operated parking brake-by-wire systems that interfaces with various elements and systems of a motor vehicle which is capable of processing information obtained from vehicle Systems, parking brake by wire systems, and the driver/user; and using this information to prevent inadvertent and/or inappropriate operation of the parking brake-by-wire system, alerting the driver/user to potential problems associated with operation of the parking brake-by-wire system and related vehicle systems.
2. Background of the Invention
With the advent of parking brake by wire systems, parking brake systems that are engaged/disengaged by an electrical contact closure, inadvertent operation or operating the system at an inappropriate time could result in loss of control of the vehicle due to a lock-up condition of the parking brake axle, which is normally the rear axle. Parking brake activator systems such as systems described in U.S. Pat. No. 5,004,077 of Carlson et al., titled Electromechanical Parking Brake System, and U.S. Pat. No. 5,180,038 of Arnold et al., titled Electronically Controlled Parking Brake System, provide the force/power to operate a conventional mechanically operated parking brake system. These systems do not use conventional foot or hand operated controls but have electromechanical devices (motors) for operating the control mechanism (hand lever or foot pedal) for the driver/user.
Generally, prior art exists with regard to the following areas: 1) Control and Interface systems between parking brake(s) and Stop Lights; 2) Control Systems for electrically operated Parking Brakes; 3) Electronic/Electric Parking Brake(s); and 4) Illumination Systems/Designs for Shift Position Indicators.
Information on vehicle systems is available in the following reference books: 1)Modern Automotive Technology by James E. Duffy, 1994; 2) Chilton General Motors Chevy/GMC Pickups and Suburban 1980-87 Repair Manual; 3) Chilton General Motors Full-Size Trucks 1988-96 Repair Manual, and 4) Automotive Electronics Handbook by Ronald Jurgen, 1994.
True parking brake-by-wire systems such as described in U.S. Pat. No. 5,443,132 of Arnold, titled Magnetic Latch Mechanism and Method Particularly for Brakes, describe a self-contained system built into the wheel assembly that is attached to the axle. This system contains an activation mechanism and a parking brake system which share common components with the service brake system designed/built into the wheel assembly on an axle. This system only requires an electrical controller/driver (power supply and switch) for operation.
Currently, there are no viable systems that adequately control the operation of the new generation of parking brake-by wire-systems to allow the static parking brake system to operate safely in a dynamic environment. Designs of parking brake systems have tended to focus on the static designs and operation of the parking brake system, as opposed to emergency brake systems designed for dynamic operation.
The early generation of parking brake-by-wire systems were digital in nature either being fully On (i.e., applied), or fully Off (i.e., released). Parking brake-by-wire systems, electrically operated parking brake systems, such as the Magnetic Latching Parking Brake (MLPB), and other systems, such as that described by U.S. Pat. No. 5,443,132, titled Magnetic Latch Mechanism and Method Particularly for Brakes, and U.S. Pat. No. 5,180,038 of Arnold et al., titled Electronically Controlled Parking Brake System, provide the force/power to operate a conventional parking brake system. These systems do not use conventional foot or hand operated controls but have electromechanical devices (motors) for operating a control mechanism for the driver/user only requiring a switch contact closure and associated power source to operate, engage/disengage the parking brake.
Early parking brake-by-wire systems were either xe2x80x9cFully Onxe2x80x9d or xe2x80x9cFully Offxe2x80x9d and often lacked user/driver intervention/control and provided the user/operator with little or no feedback pertaining to the use, operation, or status of the system. These systems, with their digital operating nature, present some very interesting problems relating to operation of the system when the vehicle is moving or in a dynamic operating mode. For example, most systems currently do not allow modulation, partial application, or other control of the rate of application, which is necessary to stop a moving vehicle without causing xe2x80x98lock-upxe2x80x99 of the braking wheels of the parking brake system (typically the rear axle).
In contrast, the second or the new generation of parking brake-by-wire systems is capable of being modulated or partially applied to provide a controlled amount of braking. However, even with this new generation of parking brake by-wire-systems, inadvertent operation of the parking brake system can lead to unexpected braking, resulting in loss of control of the vehicle or rear-end collisions due to the lack of an interface between the parking brake-by-wire system and the stop/brake lights. Emergency situation brake requirements (service brake failure) must prevent total lock out of these parking brakes by wire systems, which would otherwise prevent their engagement during dynamic operation and thus eliminate xe2x80x98emergency brakexe2x80x99 function.
In the prior art, as long as this type of system is used as a xe2x80x98staticxe2x80x99 parking brake and is not intended to function as a xe2x80x98dynamicxe2x80x99 emergency brake, these designs and control systems and operating switches are sufficient so long as the braking system is locked-out or prevented from engaging when the vehicle is moving. However, in the rare occurrence of service brake failure, these systems need to be available as an emergency brake or dynamic brake. The lack of control of the amount of brake application force of these digital type systems has not gained acceptance by major automotive or the driver/user and generally have not been produced for vehicles.
There remains a need for a control system for a parking brake-by-wire system that interfaces with the various elements and systems of a motor vehicle; processes various information obtained from vehicle systems, parking brake-by-wire systems, and the driver/user; and uses this information to safely control the operation of the parking brake-by-wire system, alerting the driver/user to potential problems associated with operation of the parking brake-by-wire system and related vehicle systems.
Conventional brake systems contain: 1) a force/energy management converter (an initiator or parking brake pedal/lever); 2) a linkage or force transfer unit (conventional brake cables); 3) an activator (brake arm); and 4) brake, friction. The driver/user activates the parking brake pedal or lever which generates cable tension on the brake cables. These cables are connected to a brake arm at the drum or disc which applies the friction brake. This cable tension causes the brake arm to exert pressure on stationary friction material which then contacts the drum/disc holding the vehicle in place (if the vehicle is stopped). If the vehicle is moving, this static brake can be used to stop or slow the vehicle.
Brake-by-Wire Systems, whether service or parking brake, have similar components/functional elements. These functional elements are: 1) an initiator (switch operator); 2) driver (electronics control unit/module); 3) force generating system (energy pack-motor/gear-box, hydraulics, etc.); 4) force transfer system (cable, linkage, etc.); and 5) mechanical brake (friction). The initiator or switch operator provides the contact information to an electrical driver that controls/conditions electrical power that is used by the force generating system which converts electrical energy into mechanical force. The force transfer unit transfers the force generated/produced by the force generating system (motor, etc.) to the mechanical friction brake. The force transfer system may be a simple link bar or as complex as a mechanical cable with its sliding inter member and flexible conduit.
Conventional mechanical parking brake systems provide user feedback that establishes functionality and user confidence in operation of the parking brake system. Feedback factors of sight, sound, and physical sensation gives the user of these systems immediate and easily understood indications of the status and operation of these traditional systems. These feedback factors and backup/supporting systems are absent in the current brake-by-wire systems, and contribute to potential liability exposure for the manufacturers and to lack of user confidence in these new systems.
Conventional mechanical parking brake systems normally provide up to eight (8) feedback functions/factors that reassure functionality and establish user confidence in operation of the parking brake system. These feedback factors include; 1) visual position of the parking brake pedal or lever; 2) physical position of the parking brake pedal or lever before application; 3) sound, or lack of sound of the parking brake system being engaged; 4) force provided by the driver as the pedal or lever apply the parking brake; 5) characteristics of the application resistance; 6) smooth transition from the released position to the applied position; 7) release characteristics (including sound) of the release cycle; and 8) the physical position of the pedal or lever after the system is engaged.
The visual physical position of the brake pedal or lever is usually associated with the parking brake system but is also applicable to the service brake system. This sensation/stimulus is basically; xe2x80x98Is the pedal, or lever, in the position it should be?xe2x80x99 This sensation is processed by the senses to determine if the brake is applied or released in the case of a parking brake and if the system is working for the service brake.
The senses determine the physical position of the pedal or lever when applying the system. If the pedal or control is not in the position it should be, the senses detect a function problem alerting the driver/user to a potential functional problem of the system. The sound or absence of sound of the system operation provides an indication of the system functionally. If the system makes an unusual sound, it is normally associated with some type of problem with the use and operation of the system. The visual feedback, sound, and physical feedback mechanisms give the user of the system immediate and easily understood indications of the status and operation of the braking system.
It is an object of the present invention to provide a control system for an electrically operated parking brake-by-wire system that interfaces with various elements and systems of a motor vehicle that processes various information obtained from vehicle systems, parking brake by wire systems, and the driver/user using this information to safely control the operation of an electrically operated parking brake-by-wire system, alerting the driver/user to potential problems associated with operation of said parking brake-by-wire system and related vehicle systems.
A further object of the present invention is to control the operation of a parking brake-by-wire system using an electronic control system that provides advantages that include the following; 1) eliminates the possibility of inadvertent operation; 2) allows operation of the parking brake-by-wire system in a dynamic mode functioning as an emergency brake; 3) allow unimpaired operation in the static mode; 4) and warns the driver/user of impending parking brake operation and to possibly expect lock-up of the brake axle containing the parking brake system.
A further object of the present invention is to classify dynamic operation distinguishing between; 1) dynamic operation as an emergency brake in the event of service brake failure; 2) dynamic operation in an automatic mode with the microcontroller/program controlling the application rate; and 3) dynamic operation with the driver/user controlling the application of more/less braking force in a xe2x80x98servoxe2x80x99 type system. Each dynamic operating mode is accompanied with its own set of operating audio/verbal indicators.
Other objects of the control system of the present invention include preventing operation of parking brake by wire systems in a dynamic mode with a functioning service brake except for driver/user initiated over-ride operation. In addition, the present invention provides an interlock system with pre-operating conditions forming an electrically operated parking brake system that results in safer operation of the vehicle and provides for a safer operating environment for personnel around vehicles equipped with such a system.
An embodiment of the present invention includes a method and system for controlling the application and release of parking brake-by-wire systems, distinguishing between operations in the following: 1) dynamic operation with service brake failure; 2) dynamic mode with a full functioning service brake; and 3) static mode. The present invention provides for elimination of the inadvertent application of parking brake-by-wire system when the vehicle is in motion with full functioning service brake system reducing the possibility of loss of control of the vehicle due to unexpected xe2x80x9clocking-upxe2x80x9d of the parking brake axle. The present invention notifies/signals the driver/user of impending change of state of the parking brake-by-wire system and provides audio status and operational information about the system.
In addition, an embodiment of the present invention incorporates the use of a dash mounted xe2x80x98Parking Brake Unsafe Indicatorxe2x80x99 that provides the driver/user with information regarding the status of the parking brake system, indication that the system is transitioning, or of potential problems with either the supporting vehicle systems or with the parking brake system and/or electronics. Also included in an embodiment of the present invention are electrical operation of the dash mounted xe2x80x98Brakexe2x80x99 light; a new and unique optional electrical driver having a microcontroller interface to a mechanical (relay) driver; and incorporation of a dash mounted combination light indicating the initiation of an operational cycle that is reset by the completion of initiated operational cycle.
The present invention provides a method and system that eliminates, or drastically reduces, the operator/operational errors/problems associated with the use of electrically operated parking brake by wire system such as inadvertent application. This invention includes use of; 1) bi-color LEDs as switch illuminators and fault monitors; 2) allows the use of a parking brake system intended for static/stationary operation to be used in a dynamic mode as an emergency brake; and 3) establishes/sets operating preconditions for; a) apply cycle in both dynamic and static modes; and b) release cycle in both dynamic and static modes.
An embodiment of the present invention comprises an electronic control system that directly operates parking brake-by-wire systems using a built-in driver or indirectly operates a parking brake-by-wire system by controlling the operation of an external driver. The method and system of this embodiment processes a driver/user request for activation/deactivation, switch contact closure, of the parking brake-by-wire system, processes/evaluates brake operational related vehicle data, and produces the proper response. In this embodiment, direct operation of the parking brake-by-wire system includes use of an electrical driver (optional) that is capable of operating the main electrical drive (e.g., motor, solenoid, electromagnetic assembly) of the parking brake-by-wire system. Indirect operation of the parking brake-by-wire system includes use of the control system to generate the appropriate control signals to correctly operate an external electrical drive unit of the parking brake-by-wire system.
An embodiment of the present invention includes both hardware (switch), electrical circuits/components, software routines/program concepts, and program algorithm(s) for the control and operation of an electrically operated parking brake-by-wire system. This system resides between the operating switch (contact closure) for the parking brake by wire system and the parking brake by wire hardware.
The preferred embodiment provides a novel arrangement and use of circuit elements to perform the complex task of operating a remote electrically operated device in a safety related application, such as a parking brake system. The preferred embodiment includes the use of a microcontroller based electronic design that contains a monitoring system for the operation of the electronics. In addition, reliability is further assured, in the preferred embodiment, by the use of operational indicators such as a parking brake unsafe indicator mounted in the dash, operational fault indicator mounted in the dash, and other components to provide the user with assurance of proper operation and other information about the system""s functions, including indications of transitions of the electrically operated parking brake-by-wire system.
The preferred embodiment, which can be referred to as a xe2x80x9cDevice, Method, and System For Control of Electrically Operated Parking Brake by Wire Systemsxe2x80x9d or alternatively as a xe2x80x9cControl Means/System,xe2x80x9d relates to the operation of parking brake-by-wire systems in safety related applications, such as automotive parking brake systems such as described in U.S. Pat. No. 5,443,132 to Arnold; entitled: xe2x80x9cMagnetic Latch Mechanism And Method Particularly For Brakes;xe2x80x9d issued Aug. 22, 1995, which is incorporated by reference, herein. The invention may also be used in conjunction with the electronically powered parking brake disclosed in U.S. patent application Ser. No. 09/217,807, entitled xe2x80x9cDevice, Method and System for control of an Electronically Powered Parking Brake,xe2x80x9d filed Dec. 22, 1998, which is incorporated by reference, herein.
An embodiment of the invention also includes a dash mounted indicator assembly containing the xe2x80x98Parking Brake UnSafexe2x80x99 and xe2x80x98Faultxe2x80x99 indicators illuminated by bi-color LEDs. The bi-polar light emitting diode (LED) driver provides individual current limiting resistors for each color of the bi-colored LEDs, allowing the driving circuit to be optimized for each color, and the Electronics Control Unit (ECU) includes use of the layered interrupt handler and microcontroller tri-state output to provide efficient and effective use of I/O ports available.
An embodiment of the present invention further includes a Fault Monitor for the use of a differential signal pair to set and reset a latching relay and control the illumination of an indicator. This feature also includes use of a circuit to produce a fault indication upon activation of a functional operational cycle initiate circuit that is independent of the microcontroller operated electronics. The circuit features include the ability to be set with hardware and reset with software providing the user/operator with an indication on the functionality of the microcontroller and its associated operating program.
An embodiment of the present invention thus uses a cost effective combination of solid-state and mechanical components, relays, to form a hybrid electrical drive unit that is capable of generating bi-polar electrical pulse or pulse width modulated drive signals in a cost effective manner. An embodiment of the hybrid electrical drive is its ability to provides; 1) steady state electrical drive signals of bi-polar (+/xe2x88x92 or xe2x88x92/+) origin; 2) short duration pulse of bi-polar (+/xe2x88x92 or xe2x88x92/+) origin; or 3) pulse width modulated signals to operate electrically operated parking brake-by-wire system to their full potential. Further, the Hybrid Electrical Drive of an embodiment of the present invention is a fault tolerate design, requiring a minimum of two failures to disable the driver. In order to enable the external brake/clutch, the primary control circuit must have two enable signals to function properly. A direction control signal is required to enable one relay, and a master control signal is required to enable the master switch. A malfunction in the directional control circuitry does not cause activation of the external brake/clutch, but does affect operation of the unit. A malfunction in the master control does not cause activation or cause non-operation of the unit, but does ultimately affect the optimal life expectancy of the electronics. This arrangement of directional control and master control provides added operational safety and eliminates inadvertent operation due to impact on the electronics.
It is understood that there are numerous significant aspects of the invention described herein. One aspect of the present invention is the way interrupts are handled by the microcontroller within the Electronics Control Unit (ECU). Using an interrupt handler, change state detector, in association with the normal interrupts allows an infinite number of interrupts to be handled and processed. By breaking the interrupts into two levels, direct acting which will bring the microcontroller out of its xe2x80x98sleepxe2x80x99 mode when the vehicle is in its xe2x80x98standbyxe2x80x99 mode (parked with no key in the ignition) and Class II interrupts which are generated when the vehicle is in an operating mode (key in the ignition). The number and usage of interrupts is a major design element in the use of microcontrollers.
Another aspect of the present invention is the handling of Input/Output (I/O) signals. Breaking the I/O lines into two levels; Direct/Active I/O""s and Multiplexed I/O""s allows expanded use of interrupts. Input/Output signals are placed in one of two categories depending on whether they require direct access to the microcontroller when the vehicle is in a xe2x80x98standbyxe2x80x99 mode (ignition key removed for over x-minutes) or only requiring access to the microcontroller when the system is powered-up (an ignition key in ignition switch). Direct acting I/O relate to input/output to peripheral systems of the vehicle while multiplex signals relate to internal operation of the Control Means/System electronics.
Another aspect of the present invention is the Parking Brake UnSafe Indicator. Some form of indicator, dash mounted light or signal, will be used to indicate that the vehicle is equipped with an electrical parking brake system. This indicator would provide the driver with additional information concerning the operation and status of parking brake-by-wire systems.
Another aspect of the present invention is the use of a signal generated by the presence of a key in the ignition switch. The presence of an ignition key provides critical information on the status of the driver (in vehicle, for example) and provides switchable (controlled) power that is more xe2x80x98in-tunexe2x80x99 to the status of the vehicle, standby or active mode, than the status of the ignition switch (On/Off). Whether a key is in the ignition switch, or not, is a more accurate indication of the operating status of the vehicle than using the status of the ignition switch. The signal also provides a more subtle reminder to remove the ignition key when exiting, opening the driver side door.
Another aspect of the present invention is the remote input interface, which allows an outside signal for vehicle systems, security system, to activate the parking brake-by-wire system.
Additional features and advantages of the invention well be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practicing the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims as well as the appended drawings.